79 350 w/Vortec heads! Rookie builder needs advice? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 01-09-2011, 05:28 PM
jsm1847's Avatar
Registered User
 
Last photo:
Join Date: Jul 2009
Location: TX
Posts: 158
Wiki Edits: 0

Thanks: 4
Thanked 6 Times in 2 Posts
79 350 w/Vortec heads! Rookie builder needs advice?

I am building a 79 350. After much research about Vortec heads, I think am going to go with them. I am really "green" when it comes to building motors. My plan is to use what I have which is the 350 that needs rebuilding, Edelbrock 600cfm performer carb, Edelbrock performer intake, just installed RV cam (with about 5k miles on it), then bolt on the Vortecs. I think I also have shorty headers.
What I would like to get advice on is.....
To what bore do I go to? The engine builder mentioned 30 or 40 over??
I think I can only use flat top pistons, sounds right?
Will my headers work with the new Vortecs? Are the patterns different with Vortec/non-Vortec? I read something somewhere (I've been searching like crazy) that something is different.
Is it a good idea to use the intake I have? My bro in law used his by expanding the bolt hole size to take the angle of the Vortecs. Good idea/Bad??
Use same cam? It was a Summit RV cam, don't know what the specs are.
With what I do have (carb,intake,Vortec heads,headers,RV cam, fresh block 30 or 40 over), how many horses should I expect to have?
When I threw the RV cam in, it actually decreased in power! And the cam I took out was almost round!
Hey, thanks for your help! What would us rookies do without you seasoned builders!!!!!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-09-2011, 09:51 PM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,658
Wiki Edits: 0

Thanks: 15
Thanked 60 Times in 57 Posts
To answer your questions in the order you asked.
1. Have it overbored to the minimum, if it only needs to go .030 then go .030
Never have one overbored that don`t need it as it doesn`t help power any.
2. There are many piston choices. Hyper, Forged. For a basic street engine hyper pistons work fine. As for the top you have to keep compression ratio in mind. It`s a good idea to keep it in the 9.5:1 area for premium pump gas. You can go up to 10:1 with a tight quench action. A 4 valve relief flat top with Vortec heads will put you close to 10:1 depending on deck height and gasket thickness. Make sure you get a piston that has a 1.560 compression distance and not 1.540.
3. Your headers will work fine. The exhaust port flange is the same on Vortec heads.
4. Get a Vortec intake. Vortec heads have ports that are taller and at a different angle than the old school heads. Make sure you use Edelbrock gaskets.
5. You said the cam is used, did you get the lifters off and keep them in order? The lifters must go on the same lobe they were previously run on with a flat tappet cam.
When you get your block back from the machinist. Scrub the bores with strong soap and a toilet brush. Spray a paper towel with WD40 and wipe the bore, if you see gray on the towel the bore isn`t clean. Bores get impregnated with hone grit during the hone process and it`s very important to get it all out. If you changed to a RV cam and lost power it`s likely the tune wasn`t correct. If the cam you use has over .450 lift you will have to get the valve guides clearanced on the Vortec heads, otherwise interferance will occur. Use a oil with ZDDP for cam break in and keep using it there after. Flat tappet cams must have this additive to keep them from going flat.
For a cam I would use a comp cams 268H. It will give you a slightly lopey idle, but still has excellant low end and mid range response. Plus it works with a stock converter. You will need self aligning rocker arms that come stock on Vortec and older SBC heads from 1987 and up. With this package you can make around 325 horses and around 380 ft lbs of torque. It makes for a excellant street package, especially with the right rear gears.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-09-2011, 11:16 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
A few thoughts...

You mentioned your bro in law enlarged the bolt holes of his intake to fit his Vortec heads. The Vortec heads we're talking about are the '96-up SBC heads having the casting numbers (last three digits) 062 or 906.

These heads are unlike the '87 to '95 heads that had a different bolt angle on the center pairs of bolts than the '86-back heads. So a dedicated Vortec intake is required, like DV said.

Much of how a cam will perform depends on the overall tune of the engine. One especially important- and often overlooked- area is the ignition timing curve. It HAS to be optimized for a particular cam. The stock timing settings and distributor calibrations will not give you the timing curve that's needed!

Whatever is done, the engine has to be kept from "detonation", aka "pinging". This will damage the engine if excessive, and the power falls off dramatically when detonation sets in, too- so it's a definite no-no.

Most SBC engines that use Vortec heads will find 32 BTDC total timing to be just right. Initial timing can vary according to the cam, but an RV-type cam will run well around 12-16 BTDC, w/another 10-12 coming in from the vacuum advance.

The other area is carb tuning. This requires the plugs to be "read" to see what's going on inside the combustion chambers. Each plug is a tiny piece of the chamber, so they can tell you a lot about the air/fuel ratio and combustion temperature to name two.

Besides the info here and from other forums and sites, you might want to avail yourself of one or more of the books that cover rebuilding SBC engines. David Vizzard has one that's kind of dated, but covers the basics pretty well (ignore the part where he says to hammer the damper on w/a block of wood and a mallet ). It's How To Rebuild Your Small Block Chevy.

Maybe there are (by now) better titles- anyone??
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-10-2011, 12:48 AM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,658
Wiki Edits: 0

Thanks: 15
Thanked 60 Times in 57 Posts
Thanks Cobalt for catching on to what I didn`t on the heads.
So to the original poster, if there`s any doubt, Here`s a little something to remember. The name "Vortec" came out in the 80`s, and was used on 4.3 V6 and small block V8`s. These engines used "swirl vane" heads, meaning, there is a large swirl vane in the bowl of the intake port. It`s designed to swirl the incoming mixture. "Vortec" in this case means "Vortex" and Vortex means tornado, hence the name. These heads have the classic 12 bolt pattern as older heads did, however, the 4 center bolts are at a different angle.
Keep in mind, these are not Vortec heads as we know them. We call them Swirl port, swirlies, Swirl Vane, TBI heads, all kinds of names. These are the worst flowing heads in small block history. They create great low end torque and throttle response, but because of the swirl vane, they choke off at 3500 RPM. The Velocity created by the upper RPM level can`t flow fast enough due to the restriction of the swirl vane so the cylinder gets choked of air and fuel. Sure, the engine will rev to 5500, but won`t make any power past 4000 RPM. Vortec heads, as we know them, are 1996 and up castings that came on L31 350`s and by shock, they have the same name. Vortec.
They have the two casting numbers that Cobalt mentions, 062 and 906.
These heads have a 8 bolt pattern that is straight up and not at a angle.
They don`t have a center heat riser passage, they also don`t have a swirl vane. Why I mention all this is because sometimes people put "Vortec" heads for sale, and they are swirl port heads. As long as the buyer don`t know the difference, which is what the seller is counting on, the seller makes a nice wad on worthless heads and the buyer walks away thinking he`s got a set of high performance heads. That`s why it`s important to always do your home work, always know what your buying.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-10-2011, 01:00 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Good stuff.

One way to tell the good Vortec heads from any other SBC heads, is by the chamber shape. The only other SBC production head w/a similar shape is the '92-'97 Gen II SBC, made in aluminum and cast iron depending on the application. The Gen II engines have reverse cooling, so you'll still need to verify what you're looking at.

But you'll be able to eliminate 99% of the non-Vortec heads by simple looking at the chamber shape:


VORTEC HEAD ON RIGHT Note the "heart" shape

Last edited by cobalt327; 01-10-2011 at 01:09 AM. Reason: Add photo.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 01-12-2011, 07:44 AM
jsm1847's Avatar
Registered User
 
Last photo:
Join Date: Jul 2009
Location: TX
Posts: 158
Wiki Edits: 0

Thanks: 4
Thanked 6 Times in 2 Posts
Thanks for the info gentlemen. A couple more questions though. Is 325 hp a good number or would taking a few more steps push me closer to 400 hp? Like I said, just trying to do my homework and reading a bunch. Lots articles mention a 400 hp build, but they are using a vortec block with ???? I'm not sure how that block is much different then mine or how that block may be better. I'm not even sure I want 400 hp. Just a mean sounding motor that should be able to burn some rubber, and take down most things on the road.
Although the articles I am reading on chevy performance website are good, I have tons of questions. So again, I appreciate you all taking the time out!!
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-12-2011, 08:00 AM
V8 Super Beetle's Avatar
VW makes it, Chevy shakes it..
 
Last photo:
Join Date: Jan 2008
Location: Houston, TX
Age: 33
Posts: 1,245
Wiki Edits: 0

Thanks: 5
Thanked 0 Times in 0 Posts
325 is a good number. It just depends on how you plan to use the motor. 400 is pretty much almost a standard hp rating when it comes to building a vortec headed 350. At least that's what most shoot for and it can be done easily but you have to select your parts carefully. For example, RPM style intake instead of the performer, 750 carb instead of a 600, and a camshaft that will allow the motor to breath in more air instead of the RV cam.

There's really little to no difference between the block you have compared to what they use in the articles. The only major differences would be a roller block verses a flat tappet block. Still, 400 is easily done with either block.

If you do decide to shoot for 400 hp, you will naturally have a mean sounding motor and it will beat most rides on the road.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
putting 305 vortec heads on an pre-vortec 350 thor1022 Engine 11 01-12-2011 03:17 PM
Will a intake off vortec heads fit non-vortec heads nobody_1250 Engine 13 12-27-2010 05:02 AM
engine builder advice crowerjunky Engine 2 10-24-2009 05:24 PM
Rookie Impala Builder ImpalaJay Introduce Yourself 6 10-20-2006 04:10 PM
Rookie Rod Builder moparist Introduce Yourself 2 03-02-2006 11:15 AM


All times are GMT -6. The time now is 07:10 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.